Brazilian President Dilma Rousseff and her German counterpart Angela Merkel issued the joint declaration in Brasilia, where the German chancellor described Brazil as "key" to controlling greenhouse gases.
Rousseff called climate change "one of the great issues of the 21st century" and said the joint declaration reflected their "commitment toward the success" of the UN summit planned for December in Paris.
With its giant but vulnerable jungle and history of large-scale deforestation, Brazil is a central player in the talks where governments will try to strike a landmark deal on reducing damaging carbon emissions.
She praised Brazil's work to halt what was once runaway forest clearance for new agricultural lands in the Amazon rainforest, even if the rate of destruction has picked up again this year, according to NGOs that monitor the Amazon.
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"We are very satisfied that there have been very ambitious developments concerning the stopping of deforestation," Merkel said.
The protection of the Amazon is not just vital to Brazil's climate policies but to the entire globe's, she added.
"It's also the key to maintaining biodiversity in the world, because Brazil is the richest country in the world concerning biodiversity," she said.
German government sources said that 550 million euros are being made available to Brazil to help its anti-deforestation and energy efficiency programs over the next two years.
The two countries have also agreed to a separate German-funded program for protection of certain areas in the Amazon.
In Brussels, EU Commissioner Miguel Arias Canete urged Brazil, along with Argentina, India, Indonesia and other big countries, to immediately submit targets for emissions reductions ahead of the summit.
In March, the European Union, the world's third biggest emitter, became one of the first blocs or countries to formally submit its pledge to the United Nations.